Dielectric composition of halogenated aromatic compound and aluminum isopropylate asa corrosion inhibitor



DIELECTRIC COMPOSITION OF HALOGENATED AROMATIC COMPOUND AND ALUMINUM ISOPROPYLATE AS A CORROSION INHIBITOR Filed Oct. 9, 1948 Aug. 28, 1951 E. E. HARDY ETAL DIELECTRIC CONTAINING METAL HALOGENATED ORGANIC ELEC RODES COMPOUND AND ALUMINUM ISOPRO PYLATE AS CORROSION INHIBITOR FIG. 4

METAL FOIL PAPER TNPREGNATED wnn HALOGENATED ORGANIC COMPOUND AND connosmn mmanon Edgar E. Hardy FIG 3 Robert J. Slocombe mmvrm ATTORNEY Patented Aug. 28, 1951 DIELECTRIC COMPOSITION OF HALOGEN- A'I'ED AROMATIC COMPOUND AND ALU- MINUM ISOPROPYLATE AS A CORROSION INHIBITOR Edgar E. Hardy and-Robert J. Slocombe, Annieton, A Ia., assignors to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware Application October 9, 1948, Serial No. 53,696

13 Claims.

The present invention relates to novel compositions of matter comprising halogenated organic compounds and aluminum isopropylate as a scavenging or corrosion inhibiting material. More specifically, the invention relates to apparatus, particularly electrical apparatus such as capacitors, transformers, circuit breakers, cables and the like containing the above compositions.

Halogenated organic compounds, more particularly halogenated aromatic compounds such as chlorinated biphenyl and chlorinated naphthalene are highly useful electrical insulating materials because of their high dielectric constants, thermal stability, resistance to oxidation, nonflammability and other valuable properties. However, it has been found that when exposed to elevated temperatures and/or high voltages, they partially decompose liberating hydrogen halides which have an exceedingly deleterious action on the paper insulation and metal parts of electrical apparatus.

For example, in transformers, circuit breakers and other electrical devices in which arcing occurs, the development of hydrogen halides as a result of the above decomposition presents a serious problem as they decrease the dielectric strength of the composition containing same and cause considerable damage by attacking paper insulation and corroding metal parts of the apparatus in which the composition is used. The undesirable effect of the above decomposition is further manifested when the above halogenated organic compounds are used as capacitor impregnants. Thus, under high operating temperatures and direct current voltages, capacitors impregnated therewith undergo a characteristic type of deterioration which results in an ever increasing leakage current, a short capacitor life, visible localized decomposition of the dielectric and corrosion of the electrodes. Moreover, in the case of capacitors operating on alternating current, the decomposition sometimes results in an excessive increase in power factor of the dielectric material.

It is, therefore, the object of the present invention to provide new compositions of matter containing halogenated organic compounds wherein the above objectionable properties are either completely eliminated or substantially reduced.

An additional object is to provide transformers, capacitors, circuit breakers, cables and the like containing halogenated organic compounds in combination with a corrosion inhibitor or scavenger whereby the delerious action of hydrogen 2 halides on the paper insulation and metal parts thereof is eliminated or materially reduced.

Another object is to provide a capacitor impregnant containing halogenated organic compounds and a corrosion inhibitor or scavenger, whereby the deleterious effect of hydrogen halides on the electrodes and paper insulation of capacitors is substantially reduced or completely eliminated with the result that the capacitor has a longer useful life and greater dielectric stability than similar capacitors not containing the corrosion inhibitor.

A further object is to provide the cellulosic insulation in transformers containing liquid halogenated organic compounds with protection against rapid destruction by hydrogen halides evolved as the result of a minor are within the transformer, thus permitting complete repair of the assembly by rapid replacement or removal of the particular part that gave rise to the arc and thereby avoiding destruction of the entire paper insulation of the transformer with a consequent high cost of repair.

A still further object is to provide switches, cables and the like containing halogenated organic compounds and a corrosion inhibitor or scavenger which practically eliminates the rusting and corrosion normally accompanying the use of such devices filled with halogenated organic compounds per se.

Other objects and advantages of the present invention will'become apparent to those skilled in the art as the description proceeds.

We have discovered that halogen decomposition products can be rendered substantially innocuous and the above objectives accomplished if, in accordance with the present invention, the halogenated organic materials to be protected are associated with a relatively small amount of aluminum isopropylate. This compound possesses the surprising property of inhibiting the deleterious action of hydrogen halides on metals and organic insulation materials without materially affecting the electrical properties of the halogenated compound or composition with which it is incorporated.

For a more complete understanding of the present invention, reference is made to the accompanying drawings and the experimental data hereinafter presented in the specific examples.

Figure 1 is a front elevation partly in section of a transformer; Figure 2 illustrates a switch in a similar manner; Figure 3 represents a rolled capacitor; Figure 4 shows a sectional view of a portion of the electrodes and dielectric sheets of Figure 3; and Figure 5 is a side view of a cable,

the following proportions.

Parts by weight Chlorinate biphenyl (60% Cl) 60 Trichlorbenzene 40 Aluminum Isopropylate 0.1

Other well known liquid halogenated hydrocarbons or mixtures thereof may be used as the insulating and cooling liquid and various other halogenated organic compounds may constitute a part of such compositions, such as for example. halogenated compounds of naphthalene, toluene, benzene, nitro-diphenyl, diphenyl oxide, diphenyl ketone. diphenyl methane, diphenyl ethane, terphenyls, quaterphenyls, etc.

The presence of 0.05 to 0.1 part by weight of aluminum isopropylate in the cooling and insulating liquid will not only substantially reduce the deleterious effect of such liquid on organic insulation but will also greatly reduce the corrosion of the metal parts of the transformer which come in contact therewith in the presence or absence of air.

The switch shown in Figure 2 comprises a casing 6', fixed contacts 1 and 8, and movable contacts 9 and I0 which cooperate therewith. The movable contacts are mounted upon a support I I which in turn is operatively connected to actuating levers l2. The following is illustrative of a suitable arc quenching liquid which may be used in this device, it being understood that the invention is not limited thereto.

' Parts by weight Chlorinated biphenyl (55% Cl) 80 Trichlorbenzene 20 Aluminum isopropylate 0.05

In the operation of electric switches, the unavoidable arcing which accompanies make-andbreak of the switch contacts results in partial decomposition of the chlorinated biphenyl or other halogenated organic compounds. The presence of aluminum isopropylate in the above liquid renders the halogen decomposition prod-- ucts innocuous with the result that switches provided therewith are substantially free from the corrosion normally accompanying the use of such devices filled with halogenated organic compounds per se.

The capacitor shown in Figur 3 is made up of alternate layers of metal foil such as aluminum or tin foil separated by sheets of dielectric material. It is produced by interleaving two dielectric sheets, such as linen or kraft paper, with the metal foil, and rolling the interleaved sheets in the conventional manner. The rolled capacitor is then impregnated with the dielectric composition by any suitable process, such as vacuum impregnation, with chlorinated biphenyl having dissolved therein a small proportion of aluminum isopropylate. The capacitor is then placed in a protective case or otherwise used as desired.

The following range of compositions is illustrative of suitable capacitor impregnants:

Composition I Per cent by weight Liquid chlorinated biphenyl, particularly chlorinated biphenyl containing from 42% to 60% by weight of chlorine s Conventional chlorinated organic dielectric materials about -0 Aluminum isopropylate 0.01-1

Composition II Parts by weight Chlorinated biphenyl (42%60% Cl) 75 Trichlorbenzene 25 Aluminum isopropylate 0.1'

Of the above range of compositions, the preferred capacitor impregnant is one having the following composition:

Parts by weight Chlorinated biphenyl (55% Cl) 75 Trichlorbenzene 25 Aluminum isopropylate 0.1

The presence of aluminum isopropylate in chlorinated biphenyl or other halogenated organic compounds provides excellent protection against the deleterious action of halogen decomposition products on metal, paper and other organic insulation material and consequently capacitors provided therewith will have a longer useful life and greater dielectric stability than similar capacitors containing halogenated organic compounds per se. Moreover, capacitors containing the above compound will not exhibit an ever increasing power factor with time when operated at high temperatures and voltages as is typical of capacitors impregnated with halogenated organic materials which are not associated with one of the above corrosion inhibitors.

Figure 4 shows a section of one turn of the finished rolled capacitor illustrating the alternate electrodes and dielectric layers. In accordance with the present invention, the finished capacitor contains a halogenated organic compound, preferably chlorinated biphenyl, and a minor proportion of aluminum isopropylate.

The cable of Figure 5 comprises a core i3, cable conductors l4, insulation consisting of paper or other suitable material 15 and a casing IS. The space between the insulated conductors and the casing is filled with a mixture of aluminum isopropylate and any of the liquid chlorinated organic compounds mentioned above. Such a composition may consist of a mixture of the following ingredients, but it is to be clearly understood that the invention is not restricted thereto.

Parts by weight Chlorinated biphenyl (60% Cl) 50 Trichlorbenzene 50 Aluminum isopropylate about 0.1

protection it aifords paper against attack by hydrogen chloride and the degree of attack is indicated by the extent to which the tensile strength or the paper is decreased. This will be rendered more apparent by reference to the following examples.

Example I Tensile strength oi paper samples- 46.2 lbs/in.

Example II Six strips or the same piece or manila wrapping paper (7" x 1") were allowed to soak at a temperature of 75 C. for 1% hours in an HCl saturated solution consisting of 60 parts by weight or chlorinated biphenyl (60% Cl) and 40 parts by weight or trichlorbenzene and at the end of this operation, the papers were soaked for minutes in benzene, another 15 minutes in methanol and dried. Alter cutting one half inch from each end of the dried paper strips, they were subjected to the above tensile strength tests with the following result:

Tensile strength of impregnated paper samples 11.5 lbs/in.

These examples demonstrate that HCl had a highly deleterious action on the samples since the tensile strength or the pap a d f 46.2 lbs/in. to 11.5 lbs./in., a decrease in tensile strength 01' approximately.75%.

Example III The foregoing example was repeated using samples 01' the same paper and the same impregnant except that 0.1 part by weight of aluminum isopropylate was added. The tensile strength of the impregnated paper was found to be 22.5 lbs./in., thus demonstrating that the above compound is a highly effective material for rendering halogen decomposition products such as HCl innocuous to paper or other fibrous organic dielectrics.

The following table illustrates the electrical properties or the dielectric composition consisting of 60 parts by weight of chlorinated biphenyl (60% Cl) and 40 parts by weight oi trichlorbenzene and also shows the efiec't thereon of adding 0.1 part by weight or aluminum isopropylate.

The above experimental data indicate that aluminum isopropylate does not seriously aflect, but actually improves, the electrical properties of the halogenated organic compounds associated therewith and that, therefore, such compositions are eminently suitable ior'use in transformers. capacitors, switches, cables and other electrical devices.

The description of the present invention has beendirected primarily to compositions containing chlorinated biphenyl, trichlorbenzene, and aluminum isopropylate, but it is to be understood that the invention is not restricted thereto but embraces halogenated organic compounds generally. Thus, the above compound may be used as a scavenger or corrosion inhibitor i'or chlorinated naphthalene, chlorinated diphenyl ketone, chlorinated diphenyl oxide, chlorinated diphenyl methane, chlorinated diphenyl ethane, chlorinated benzene, chlorinated toluene, chlorinated nitro diphenyl, chlorinated alkylated benzenes,

chlorinated alkylated biphenyls, ethyl trichlor benzene, ethyl tetrachlorbenzene, ethyl pentachlorbenzene, chlorinated terphenyls. chlorinated quaterphenyls, chlorinated paraflinic hydrocarbons, chlorinated alicyclic hydrocarbons, chlorinated oxygen-containing organic compounds, chlorinated rubber, chlorobutadiene polymers, chlorinated fats, chlorinated vegetable oils. chlorinated animal oils, chlorinated mineral oils or mixtures of two or more or these. In place of the chlorinated compounds, the corresponding fluorine, bromine and iodine derivatives may be used. In fact, any halogenated organic compound or composition which tends by reason of its halogen content to cause corrosion of metals or dehydration of paper or organic fibrous insulation, may be rendered substantially innocuous by means of aluminum isopropylate.

The method of incorporating aluminum isopropylate varies with the halogenated organic compound or composition. It the compound or composition is liquid at room temperature, the above compound is merely dissolved therein in suitable concentrations; it it is a solid, the aluminum isopropylate is blended therewith by the use of solvents or swelling agents or by means of mixing rolls, etc. In the case of halogenated polymers, the aluminum compound may be incorporated before, during or after polymerization of the corresponding monomers.

The quantity of aluminum isopropylate used varies with the halogenated organic compound or composition. In general, satisfactory results are obtained by employing this compound in an amount varying from 0.05% to 1% and preferably from 0.05% to 0.1% by weight of the halogenated organic compound or composition, but it is to be understood that the invention is not limited thereto as slightly lower and somewhat higher concentrations may be employed. Stated broadly, the above compound may be used in amounts varying from 0.01% by weight up to and above the limit of its solubility in the halogenated organic compound or composition. In most instances, it is desirable not to exceed the solubility limits of the aluminum isopropylate, but there are some applications such as heat exchanging operations in which this may be done without harmful eil'ects. 7

As widely different embodiments of this invention may be made without departing from the spirit thereof, it is to be understood that the invention is not limited to the specific embodiments except as defined in the appended claims.

We claim:

, 1. A composition of matter consisting essentially of a halogenated aromatic compound and as a scavenger therefor a suillcientamount of aluminum isopropylate to render the decomposition products of said halogenated-aromatic compound substantially innocuous.

2. A composition 01' matter consisting essentially of a chlorinated aromatic compound and as a scavenger therefor aluminum isopropylate inan amount varying from about 0.01 by weight up to and above the limit of its solubility in said composition.

3. A heat transfer and dielectric composition consisting essentially of chlorinated biphenyl and about 0.05% to about 1% by weight of aluminum isopropylate.

4. An insulating and cooling medium for electric apparatus consisting essentially of a liquid chlorinated biphenyl and about 0.05% to about 1% by weight of aluminum isopropylate, said chlorinated biphenyl containing from 42% to 60% by weight of chlorine.

5. A dielectric composition consisting essentially of chlorinated biphenyl and about 0.05% to about 1% by weight of aluminum isopropylate, said chlorinated biphenyl containing from 42% to 60% by weight of chlorine.

6. A dielectric composition consisting essentially of chlorinated biphenyl and from 0.01% to 1% by weight of aluminum isopropylate.

7. A dielectric composition consisting essentially of chlorinated biphenyl and about 0.1% by weightot aluminum lsopropylate.

8. An insulating and cooling composition for electrical apparatus consisting essentially of a liquid chlorinated biphenyl and about 0.05% to about 0.1% by weight of aluminum isopropylate.

9. An insulating and cooling composition for electrical apparatus consisting of about 60% by weight of chlorinated biphenyl, about 40% by weight of trichlorbenzene and about 0.1% by weight of aluminum isopropylate.

10. An electric arc quenching composition con- 12. A capacitor impregnant having substantially the following composition.

Per cent by weight Chlorinated biphenyl containing from 42% to 60% by weight of chlorine O-about 100 Chlorinated aromatic hydrocarbons other than chlorinated biphenyL- about 100-0 Aluminum isopropylate 0.01-1

13. A capacitor impregnant consisting of about 75% by weight of chlorinated biphenyl (42%- 60% Cl) about 25% by weight of trichlorbenzene and about 0.1% by weight of aluminum isopropylate.

EDGAR E. HARDY. ROBERT J. SLOCOMBE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,041,594 Clark May 19, 1936 2,339,091 McLean Jan. 11, 1944 2,125,961 Shoemaker Aug. 9, 1938 2,453,493 Clark et a1. Nov. 9, 1948 2,468,544 Clark Apr. 26, 1949 

1. A COMPOSITION OF MATTER CONSISTING OF ESSENTIALLY OF A HALOGENATED AROMATIC COMPOUND AND AS A SCAVENGER THEREFOR A SUFFICIENT AMOUNT OF ALUMINUM ISOPROPYLATE TO RENDER THE DECOMPOSITION PRODUCTS OF SAID HALOGENATED AROMATIC COMPOUND SUBSTANTIALLY INNOCUOUS. 